This invention relates to pressurization systems and liquid rocket propulsion systems, and particularly to those used for attitude control or maneuvering of small space vehicles or airborne vehicles where the requirement for thrust is intermittent rather than continuous, and must be available rapidly upon demand. This invention also relates to increasing performance of such propulsion systems, by way of eliminating inert mass from the propulsion system.
Previously, small liquid propulsion systems which provide intermittent thrust on demand were pressure fed propulsion systems in which the propellant stored in the propellant storage tanks is pressurized above the operating pressure of the engines. In such a pressure-fed system, a valve connects the propellant storage tank to the engine's propellant injector, which gives the capability for thrust on demand merely by opening the valve.
High-performance liquid propulsion systems which provide a high thrust-to-weight ratio and a high fraction of stored propellant relative to inert mass are pump-fed propulsion systems. The use of pumps permits the tank pressure to be low, so the storage tanks can be lightweight. In pump-fed systems, it is typical to use rotating turbomachinery pumps which are driven by gases generated from reacted propellant. This is well-suited to propulsion systems requiring continuous, steady thrust, such as launch vehicles, for example. A limitation is that a requirement for intermittent thrust-on-demand cannot be met due to the time required to start and stop the turbo pumps and flows in the system. Thus, turbo-pump-fed propulsion systems are useful for producing thrust continuously.